NO155565B - PROCEDURE FOR AA WEEK SELECTIVITY FOR FUEL PRODUCTION OF A CRACKING CATALYST. - Google Patents

Description

The invention relates to the catalytic cracking of hydrocarbon

bonuses. More specifically, the invention relates to a method for increasing the selectivity for gasoline production of a cracking catalyst by reducing the harmful effects of contaminating deposits on the catalyst, i.e. by passivating catalyst contaminating metals.

In most common catalytic cracking processes where hydrocarbon feedstocks are cracked to produce light distillates, a gradual deterioration of the catalyst occurs.

Part of this deterioration is due to the deposition on the catalyst of contaminants found in the feed material. The deposition of these pollutants, which include nickel/vanadium and iron,

tends to have an unfavorable effect on the cracking process in the form of reduced conversion of the feed material to cracked products, reduced production of petrol and increased yields of hydrogen and coke.

It is known in the art that the adverse effects of catalyst contamination can be partially counteracted by treating the cracking catalyst with passivating agents, e.g. antimony and its compounds. Treatment of the cracking catalyst with antimony is highly desirable as all four characteristics of catalyst deterioration due to the deposition of contaminants on the catalyst show an improvement. Turnover and selectivity towards petrol increases, while the production of hydrogen and coke decreases. Other passivating agents do not result in improvement of all four characteristics of undesirable cracking behavior due to the deposition of contaminants on the catalyst. Certain passivating agents actually cause a worsening of one or more of the characteristics of unwanted cracking behaviour,

e.g. in case of reduced turnover, but they are still called passive agents because they improve another of the indicators, e.g. reduces the production of hydrogen.

Cracking catalysts resistant to the assumption of undesirable cracking behavior when contaminants are deposited on them from the feed material are highly desirable,

because they enable the economic conversion of poor quality feedstocks into gasoline and other light hydrocarbons. Because the availability of low-quality feed materials is relative

good, there is a need for new and improved passivators that impart more desirable cracking properties to contaminated cracking catalysts. There is also a need for passivating agents which confer cracking catalysts resistance to adverse effects from contamination from the feed material. Because of. environmental protection laws that may limit the use of certain passivating agents, it is also highly desirable to obtain alternative passivating agents so that contaminated oils can still be economically cracked.

One purpose of the invention is to provide a method which provides increased selectivity for petrol production by cracking hydrocarbon feed materials containing polluting metals, the effects of metal deposits on the cracking catalyst being counteracted.

This and other purposes of the present invention will appear in more detail from the following detailed description and claims.

According to one embodiment of the invention becomes

a cracking catalyst contacted with a passivating agent consisting of a tin thiophosphate as set forth in claim 1. When used for the catalytic cracking of hydrocarbons, the contacted cracking catalyst exhibits improved resistance to the deleterious effects caused by contaminants deposited on the catalyst from the feed material. When contaminants are deposited on the catalyst at the time it is contacted according to the invention, its activity and selectivity are improved and its value for catalytic cracking is instantly increased. Even cracking catalysts which, due to deposited contaminants show such poor cracking behavior that their continued use for cracking would not be economically justifiable, can be contacted according to the invention and are often used economically for cracking of hydrocarbon feed material, especially heavy oils and the like.

It has been found that a tin thiophosphate as indicated above

is particularly useful for passivating contaminants on a cracking catalyst. Such a combination of tin, sulfur and phosphorus drastically increases the cracking catalyst's selectivity for the production of a petrol fraction. If, on the other hand, a treatment of a cracking catalyst extensively deposited

metals from a hydrocarbon feedstock were treated with tin alone, the activity was reduced, although this reduction could be counteracted by the use of antimony in combination with tin. It has now surprisingly been found that the treatment of the cracking catalyst with a compound containing tin as well as sulfur and phosphorus, more specifically the tin thiophosphates specified in claim 1, drastically increases the cracking catalyst's selectivity for the production of products in the petrol range, in addition to reducing the production of hydrogen and coke, even in the absence of antimony.

The passivating agent contains a tin source, a phosphorus source and a sulfur source. Specifically, have. there is at least one phosphorus atom and also at least one sulfur atom in the gamma position or closer to the tin. Or put another way, the agent has at least one sulfur atom which is in the alpha, beta or gamma position in relation to the tin, and at least one phosphorus atom which is in the beta position in relation to the tin. These treatment agents can be conveniently expressed by the formula

where R are the same or different and each comprises a hydrocarbyl radical with 1-24 carbon atoms, X is selected separately from oxygen and sulphur, with at least one X being sulphur, and n being 2 or 4. The total number of carbon atoms per molecule can vary from 4 to approx. 200. The most preferred tin compounds in this class are those which have the above formula where the R groups are alkyl radicals with 2-10 carbon atoms per radical, e.g. n-propyl, because it has been tested with good results. The R groups can also comprise substituted or unsubstituted C₁- or C₁-cycloalkyl radicals and substituted and unsubstituted phenyl radicals. Examples of suitable R-radicals are ethyl, n-propyl-, isopropyl, n-, iso-, sec- and tert-butyl, amyl, n-hexyl, isohexyl, sec-hexyl, n-heptyl, n-octyl, isooctyl , tert-octyl,

dodecyl, octyldecyl, cyclopentyl, methylcyclopentyl, cyclohexyl, methylcyclohexyl, ethylcyclohexyl, phenyltolyl, cresol, ethylphenyl, butylphenyl, aarylphenyl, octylphenyl, vinylphenyl and the like. Preferably, the hydrocarbyl radicals are bound to phosphorus via an oxygen atom, because such compounds can be prepared by reacting an alcohol, e.g. n-propanol, with phosphorus pentasulfide to give an O,0-dihydrocarbyl-phosphordithio acid, and reacting this acid or a salt thereof with a suitable tin compound to produce the tin salt. These compounds are conveniently represented by the formula

where R and n are as indicated above.

These treatment agents are preferred because they are very effective passivating agents, easy and inexpensive to produce, and because they its oil solubility is well suited for dissolution in hydrocarbon feed materials and continuous dosing into a cyclic cracking process. Examples of the most preferred treatment agents are: tin(II)0,0-diethyl-dithiophosphate (in the following, dithiophosphate is also called phosphorus dithioate), tin(IV)0,0-diethyl-dithiophosphate, tin(II)0,0- di-n-propyl-dithiophosphate, tin(IV)0,0-di-n-propyl-dithiophosphate, tin(II)0,O-diisopropyl-dithiophosphate, tin(IV)0,0-diisopropyl-dithiophosphate, tin( II)0,O-di-n-butyl-dithiophosphate, tin(IV)0,0-di-n-butyl-dithiophosphate, tin(II)0,0-diisobutyl-dithiophosphate, tin(IV)-0,0 -diisobutyl-dithiophosphate, tin(II)0,0-di-sec-butyl-dithiophosphate, tin(IV)0,O-di-sec-butyl-dithiophosphate, tin(II)0,0-di-tert-butyl -dithiophosphate, tin(IV)0,O-di-tert-butyl-dithiophosphate, tin(II)0,0-diamyl-dithiophosphate, tin(IV)0,0-diamyl-dithiophosphate, tin(II)0,0 -di-n-hexyl-dithiophosphate, tin(IV)0,0-di-n-hexyl-dithiophosphate, tin(II)0,0-di-sec-hexyl-dithiophosphate, tin(IV)0,0-di -sec-hexyl-dithiophosphate, tin(11)0,0-di-n-heptyl-dithiophosphate, tin(IV)0,0-di-n-heptyl-dithiophosphate, tin(II)0,0-di-n -octyl-dithiophosphate, tin(IV)0,0-di-n-octyl-dithiophosphate, tin(11)0, O-diisooctyl dithiophosphate, tin(IV) 0,0-diisooctyl dithiophosphate, tin(II) di-tert-octyl dithiophosphate, tin(IV) 0,0-di-tert-octyl dithiophosphate, tin(II) 0,0-didodecyl-dithiophosphate, tin(IV)0,0-didodecy1-dithiophosphate, tin(11)0,0-dioctyldecy1-dithiophosphate, tin(IV)0,0-dioctyldecy1-dithiophosphate, tin(11)0, 0-dicyclopentyl dithiophosphate, tin(IV)0,0-dicyclopentyl dithiophosphate, tin(II)0,0-dimethylcyclopentyl dithiophosphate, tin(IV)0,0-dimethylcyclopentyl dithiophosphate, tin(II)0,0- dicyclohexyl-dithiophosphate, tin(IV)0,0-dicyclohexyl-dithiophosphate, tin(11)0,0-dimethylcyclohexyl-dithiophosphate, tin(IV)0,0-dimethylcyclohexyl-dithiophosphate, tin(II)0,0-diethylcyclohexyl- dithiophosphate, tin(IV)-0,O-diethylcyclohexyl dithiophosphate, tin(11)0,0-diphenyltoluyl dithiophosphate, tin(IV)0,0-diphenyltoluyl dithiophosphate, tin(II)0,0-dicresol dithiophosphate , tin(IV)0,0-dicresol-dithiophosphate, tin(II)-0,0-diethylphenyl-dithiophosphate, tin(IV)0,0-diethylphenyl-dithiophosphate, tin(II)0,0-dibutylphenyl-dithiophosphate, tin(IV)0,0-dibutyl-phenyl-dithiophosphate, tin(II)0,0-diamylphenyl-dithiophosphate, tin-(IV)0,0-diamylphenyl-dithiophosphate, tin(II)0,0-dioctylphenyl-dithiophosphate, tin(IV)0,0-dioctylphenyl-dithiophosphate, tin (II) 0,0-divinylphenyl-dithiophosphate and tin(IV) 0,0-divinylphenyl-dithiophosphate.

Of these compounds, tin(II) 0.0-di-n-propyl phosphordithioate and tin(IV) 0.0-di-n-propyl phosphordithioate are most preferred because they have been tested with good results and are relatively stable.

The tin/phosphorus and tin/sulphur ratios in these compositions can be varied by using tin(IV) or tin(II) salts of the dihydrocarbylthiophosphoric acids. E.g. tin(IV) 0,0-di-n-propyl phosphorodithioate can be prepared by reacting a suitable tin compound, e.g. stannous chloride with 0.0-di-n-propyl-dithiophosphoric acid, or preferably a salt thereof, e.g. potassium dipropyl dithiophosphate, in a suitable solvent, e.g. tetrahydrofuran. Tin(II) 0,0-di-n-propyl phosphorodithioates can be prepared by a double decomposition reaction between a tin(II) carboxylate, e.g. tin(II) octanoate, and the thiophosphoric acid, e.g. 0,0-di-n-propyl phosphorodithioic acid dissolved in cyclohexane. The tin salt produced in this way can be effectively used to treat metal-contaminated catalysts for fluid catalytic cracking, without removing the free carboxylic acid it contains.

Compositions which are represented by the formula stated above can thus have tin/phosphorus ratios, tin/sulphur ratios and phosphorus/sulphur ratios that vary over wide areas. Treatment of cracking catalysts with tin as well as phosphorus and sulfur according to the invention effectively reduces the harmful effects on the cracking process as a result of metal contamination on the cracking catalyst, in particular the catalyst's reduced selectivity for petrol.

When using the invention, a cracking catalyst is brought into contact with a passivating amount of a tin source and a catalyst promoting amount (promoting amount) of both a phosphorus source and a sulfur source. By a passivating amount of tin source shall be understood an amount sufficient to obtain at least one improvement selected from the group consisting of an increase in catalyst activity, an increase in the selectivity of the catalyst for products in the gasoline range,

a reduction in coke production and a reduction in hydrogen production. A catalyst-promoting amount is to be understood as an amount that contributes to at least one of the above-mentioned improvements, and/or provides at least one further improvement, the improvement or the property being further promoted being greater than the improvement that is the result of bringing the cracking catalyst into contact with the sulfur and phosphorus source in an equal amount, without the cracking catalyst being brought into contact with the passivating amount of tin source. The cracking catalyst is preferably contacted with a sufficient amount of the phosphorus source and the sulfur source in addition to the tin source to provide an increase in the selectivity of the cracking catalyst for cracking the feedstock to gasoline range products.

Generally, the cracking catalyst is contacted with a sufficient amount of tin to impart to the cracking catalyst a tin concentration of 0.0001-4 weight percent tin based on the weight of the tin-treated cracking catalyst. More commonly, the cracking catalyst is contacted with a sufficient amount of tin to give it 0.001-2 weight percent tin based on the weight of the tin-treated cracking catalyst.

A tin concentration on the cracking catalyst of 0.005-1 weight percent tin based on the weight of the tin-treated cracking catalyst is a more preferred amount of tin for economic reasons, while tin concentrations of 0.01-0.15 weight percent based on the weight of the tin-treated cracking catalyst are most preferred because they match carefully with the tin concentrations that have been tested with good results. The sulfur concentration ration should be 0.5-8 parts by weight of sulfur for every part by weight of tin. The phosphorus concentration should be 0.25-1 part by weight of phosphorus for each part by weight of tin. The ratios are not exact, as they are based on the approximation that phosphorus or sulfur has an atomic weight of approx. the fourth part of the tin. Normally, the passivating agent will contain one part by weight or less of phosphorus and 1-4 parts by weight of sulfur for every part by weight of tin.

Treatment of the cracking catalyst with the passivating agent results in a reduction of the harmful effects of metal contaminants on the cracking catalyst. The treated catalyst can be used directly for catalytic cracking without first being subjected to a heat treatment. New cracking catalyst can also be treated to reduce the tendency to adverse effects from deposits of contaminants from the feed material.

When the invention is used for the reactivation of used cracking catalysts, it is desirable to maintain a ratio between tin and contaminants of 0.2:100 - 200:100, calculated as the weight ratio between metallic tin and the total weight of vanadium and four times the weight of nickel on the catalyst. The combined weight of vanadium and four times the weight of nickel on the cracking catalyst is usually referred to as the vanadium equivalent, and as used herein is expressed as a combination of parts vanadium and four times nickel per million parts by weight cracking catalyst including vanadium and nickel (ppm). A preferred ratio between tin and vanadium equivalents on the cracking catalyst is from approx. 0.5:100 to approx. 50:100, because conditions within such an area have been tested with good results.

A number of methods can be used to bring the cracking catalyst into contact with the passivating agent. When the cracking catalyst is brought into contact with solids,

these can be mixed in finely divided form with the cracking catalyst in the usual way, e.g. by rolling, shaking, stirring and the like. Alternatively, these sources can be dissolved or dispersed in a suitable liquid, e.g. water, hydrocarbon or aqueous acid, depending in part on the particular agent employed, and the resulting solution or dispersion may be used to impregnate the cracking catalyst, followed by evaporation of the liquid, or the source may be precipitated onto the catalyst from a solution of the source followed by removal of the solvent, or source can be sprayed onto the catalyst. When an oil-soluble agent is used, the preferred method of contacting the agent with the cracking catalyst is to dissolve or disperse the selected agent in the hydrocarbon feedstock to be used in the cracking process. If desired, the cracking catalyst can also be exposed to the agent in vapor form for deposition of the source on the catalyst. Combinations of the different methods can of course be used.

The passivating agent can be brought into contact with used cracking catalyst, unused cracking catalyst or mixtures thereof according to the invention, and before and/or during the use of the catalyst. Treatment of spent cracking catalyst with the agent increases the catalyst's selectivity for gasoline production and reduces the production of hydrogen and coke, often without harming catalyst activity. Treatment of new cracking catalysts with the agent contributes to maintaining high catalyst selectivity for petrol production and low production of hydrogen and coke. The term "cracking catalyst" as used herein refers to both new and used cracking catalyst materials useful for cracking hydrocarbons in the absence of added hydrogen.

Cracking catalysts which are suitable for treatment according to the invention can be any of the cracking catalysts used for the catalytic cracking of hydrocarbons which boil at a temperature above 204°C in the absence of added hydrogen, for the production of petrol, mixing components for motor fuel and light distillates. Because of. the high activity and selectivity of zeolite-containing cracking catalysts, these are preferred. The zeolite-containing materials can be naturally occurring or synthetic. In general, they have been at least partially ion-exchanged with ammonium or rare earth cations. Zeolite-modified silica/alumina catalysts are particularly well suited for treatment according to the invention, especially such catalysts which comprise 1-50% by weight of zeolite-containing materials. Examples of cracking catalysts that are useful in the present invention include e.g. hydrocarbon cracking catalysts obtained by mixing an inorganic gel of an oxide with an aluminosilicate, and aluminosilicate compositions that are strongly acidic as a result of treatment with a fluid medium containing at least one rare earth metal cation and one hydrogen ion or an ion that can be converted into a hydrogen ion.

The catalytic cracking materials can vary with respect to pore volume and surface area. In general, the unused cracking catalyst will have a pore volume in the range of 0.1-1 ml/g. The surface area of this unused cracking material will generally be in the range of 50-500 m 2 /g. The unused cracking material that is used will generally be in particle form with a particle size that is mainly in the range of 10-200 micrometres.

Feed materials which are suitable for conversion by the treated cracking catalyst according to the invention are generally oils with an initial boiling point of over 204°C. These include gas oils, fuel oils, peaked crude oil, shale oil, waste polymers in solvents and oils from coal and/or tar sands. The feed materials can contain, and usually do contain, significant concentrations of at least one metal selected from nickel, vanadium and iron. The presence of such metals usually adversely affects the selectivity and activity of the catalyst. As these metals are concentrated in the least volatile fractions of oil which are suitable for use as feed material, cracking of the heavy oil fractions is probably the most important application for the treated cracking catalyst according to the invention. Such feed materials can e.g. contain nickel concentrations of approx. 100 ppm, vanadium concentrations of approx. 500 ppm and iron concentrations of approx. 500 ppm. Because nickel has a stronger effect on the cracking catalyst's activity and selectivity than vanadium and/or iron, it is often convenient to refer to the total impurities in the feed material as parts by weight per million total active metals. As the term "total active metals" is used herein, it means the sum of vanadium and iron and four times the weight of nickel expressed as parts per million by weight of the feed material (ppm).

Most known industrial cracking processes for heavy oil can crack heavy oils with a metal content of up to approx. 100 ppm total active metals as defined above. Economically marginal results are achieved with oils that have 50-100 ppm total active metals. According to the present invention, heavy oils with a total metal content of approx. 50-100 and even those with 100-200 ppm and higher total metals are cracked in a cracking process using the treated cracking catalyst as noted above to provide gasoline and other fuels and fuel blending components. Heavy oils with a total metal content of 100-300 ppm which cannot be used directly for fuel production in most known processes and especially not for the production of petrol or higher-boiling hydrocarbon fuels, can thus, according to the invention, be cracked to give petrol and higher-boiling hydrocarbon fuels such as petroleum , diesel fuel and heating oils.

It is preferred to dose the passivating agent into the catalytic cracker together with the feed material at a rate which at least corresponds to the amounts of contaminants in the feed material as indicated below:

Higher speeds can of course be used if desired, e.g. when it is desired to increase the concentration of tin on the cracking catalyst.

A preferred embodiment of the cracking process uses cyclic flow of catalyst from a cracking zone to a regeneration zone. In this process, the hydrocarbon feed material is brought into contact with a fluidized cracking catalyst in a cracking zone under cracking conditions in the absence of supplied hydrogen, a cracked product is obtained and withdrawn, the cracking catalyst is fed from the cracking zone into a regeneration zone, and in the regeneration zone the cracking catalyst is regenerated by it is brought into contact with a gas containing free oxygen, preferably air. The coke that has built up during the cracking process is thereby at least partially burned away from the catalyst. The regenerated cracking catalyst is reintroduced into the cracking zone, usually after it has been supplemented with make-up catalyst.

Such cyclic catalytic cracking processes are well known to those skilled in the art. In general, the cracking reaction takes place in the presence of fluidized cracking catalyst at catalytic cracking temperatures, e.g. temperatures of 482-593°C, typically 504-549°C at catalytic cracking pressures, e.g. pressure of 138-448 kPa, usually 207-345 kPa. In general, the cracking catalysts used contain zeolitic materials. The contact between catalyst and feed material generally takes 1-4 seconds, and is carried out with a weight ratio between catalyst and feed material of 4:1-15:1. Regeneration is carried out under catalyst regeneration conditions, e.g. in the presence of oxygen-containing gas at temperatures of 427-871°C, usually 621-732°C for a period of 3-30 min. and which is sufficient to reduce the concentration of coke on the catalyst to less than 0.3 weight percent, preferably less than 0.1 weight percent.

A better understanding of the invention will be obtained from the following examples which are intended to illustrate the preferred embodiments, and which also include a number of comparative examples.

Example 1

Synthesis of tin( IV) 0, O- dihydrocarby1- phosphorus dithioates

This compound is produced by a double decomposition reaction (or metathesis) between a tin (IV) salt and dihydrocarbyl phosphorodithioic acid, or preferably a salt of the acid and an element from group Ia or Ila in the periodic table, e.g. lithium, sodium, potassium, magnesium and calcium. In the anion of the phosphorus bond [(RO) 2^2], R is a hydrocarbyl radical with 1-24 carbon atoms, and R can be an alkyl, cycloalkyl, alkenyl, cycloalkenyl or aryl radical or a combination of these radicals, e.g. alkaryl, aralkyl etc. Examples of suitable hydrocarbyl radicals are methyl, normal and isopropyl, normal and branched hexyl, decyl and octadecyl, cyclohexyl, cyclohexenyl, phenyl, xylyl, 1- and 2-anthra-cyl and the like.

Suitable tin(IV) salts for the double decomposition reaction are generally those which are soluble in the solvent selected as reaction medium. Examples are the tin halides, especially the chlorides, bromides and iodides and tin (IV) sulphate.

Solvents suitable for carrying out the synthesis of tin dihydrocarbyl phosphorodithioate are those in which the reactants and the tin product are soluble, at least to some extent. Examples are water and polar organic compounds such as methanol and ethanol, tetrahydrofuran, acetone and the like, and mixtures thereof. The reaction conditions for the synthesis are not critical. The temperature for the reaction can generally vary from 0°C to 75°C, for the sake of simplicity ambient temperatures are preferred. The reaction seems to be similar to ion reactions in terms of the speed. Consequently, long reaction times are not necessary, although a time of 2-3 hours can be used at the lower limit of the indicated temperature range. At approx. 25°C and above, the reaction can be considered complete when the reagents have been combined, but additional time can be used to allow phase separation of the products, e.g. oil from aqueous solution or inorganic salts from organic solvents. The order in which the reagents are combined is not critical, i.e. the tin salt can be added to the phosphorus-containing reagent or vice versa. And since the reaction is not equilibrium limited, the preferred ratio for combining the reactants is the stoichiometric ratio. (This is not the same as quantitative yields being obtained, as non-productive reactions may take place, e.g. between the tin compound and the solvent.) Although the amount of solvent in which the reaction takes place is not critical, it will suitable to be at least approx. one liter per gram molecule total reactants. Preferably, there will be sufficient solvent to completely dissolve the reactants.

For many purposes, including the preparation of a metal-contaminated cracking catalyst passivator, it is necessary to separate the desired product from the byproduct of the double decomposition reaction. When water is the solvent, this can conveniently be carried out by separating the product which is present as an insoluble oil. When any of the above-mentioned organic solvents are used, the resulting inorganic salt is precipitated and can be separated by filtration, centrifugation, etc.

The following illustrates the synthesis of tin(IV) di-n-propyl phosphorodithioate: To a solution of 3.51 g (10 mmol) SnCl4<*>5H20 in approx. 50 ml tetrahydrofuran (THF) was added dropwise to a solution of 10.10 g (40 mmol) potassium di-n-propyl phosphorodithioate in approx. 50 ml of THF. The solution immediately turned bright yellow, and potassium chloride was precipitated. The mixture was heated to 65°C for 30 min, cooled to room temperature and filtered to remove the potassium chloride. THF was removed from the filtrate by a rotary evaporator and the residue was treated with approx. 50 ml n-hexane, this solution was again filtered to remove unreacted reagents and finally n-hexane was removed from the product by a rotary evaporator. The yield of the product was 7.15 g, which was 74% of the theoretical calculated yield. Elemental analyzes of the product, calculated as

<CU>„<Hc>,0QP„SoSn was 29.66% C, 5.81% H, 12.75%. P and 12.21% Sn

24 bb o 4 o

(calculated values), and 29.00% C, 5.63% H, 12.2% P and 11.7%

Sn (found).

Example II

Synthesis of tin(II) bis(di-n-propyl-phosphorus dithioate)

A solution of 25 g (0.048 mol) of tin(II) octanoate (catalyst T-9 from M&T Chemicals Inc., Rahway, NJ) in ca. 25 ml of cyclohexane was treated dropwise at approx. 25°C with 20.76 g (0.097 mol) (C3H70)2PS2H under constant stirring. The solution immediately turned orange/brown, and dark mahogany when the addition was complete. After standing for three days, the solvent was removed from the prepared product by a rotary evaporator, leaving a viscous product. By chemical analysis it was found to contain 16.3% by weight of tin.

Example III

Two commercially available cracking catalysts comprising amorphous silica/alumina and zeolite cation-exchanged with rare earth metals were used in an industrial fluid catalytic cracker until they reached equilibrium with respect to metal accumulation (the catalyst was removed from the process systems at a constant rate) and had the following characteristics:

Catalyst II contained approx. 2620 ppm vanadium equivalents.

A peaked crude oil from Borger, Texas had the following characteristics:

A gas oil from Sweeny, Texas had the following properties:

A gas oil from Kansas City had the following characteristics:

Example IV

Catalyst I was used for cracking feed material I in a laboratory-sized quartz reactor with a fluidized bed at 510°C and atmospheric pressure, with cracking periods of approx. 0.5 min and intermediate regeneration periods of approx. 30 min at approx. 649°C. The experiments were carried out with a number of different catalyst/oil ratios and the results given in Table VI are from curves calculated by regression analysis from the observed data points. In this and subsequent examples, treatment of the trial results by regression analysis is based on no less than five trials, generally at least 10 trials were used in the analysis.

The data are shown to illustrate the cracking behavior of metal contaminated catalysts used in fluid catalytic cracking at different conversion levels. The turnover is increased by increasing the catalyst/oil ratio, e.g. in that the feed rate of the oil is reduced. It should be noted that as the conversion increases, the selectivity of the cracking catalyst for gasoline production decreases, even though the gasoline yield increases. Coke and hydrogen production also increases with increased turnover.

Catalyst I was also used for cracking feed material II at different conversion levels. Results from regression analysis of these trials are shown in table VII.

A comparison of the data set forth in Table VI with that in Table VII shows that the activity of the cracking catalyst for cracking feedstock I is greater than its activity for cracking feedstock II. However, the trend shown in Table VII is the same as in Table VI. As the conversion increases, the selectivity of the cracking catalyst for converting the feed material to gasoline products is reduced, and the absolute yield of gasoline, coke and hydrogen increases.

Example V

Four samples of catalyst I were treated so that

they contained different concentrations of dibutyltin oxide. This was accomplished by combining weighed portions of dry catalyst with weighed portions of dibutyltin oxide, which had been ground to pass a 325 mesh sieve. These ingredients were mixed by shaking, and then conditioned as follows: The catalyst was placed in a laboratory-sized quartz reactor with a bounded fluidized bed, and heated from room temperature (about 20 C) to about 482 C under fluidization with nitrogen, then heated from this temperature to approx. 650°C during fluidization with hydrogen. While held at 650°C, the catalyst was fluidized for 5 min with nitrogen, followed by fluidization for 15 min in air. The catalyst was then aged by subjecting it to 10 cycles each consisting of the following treatment: The catalyst was cooled from 650°C for 30 seconds while fluidizing with air, then cooled to approx. 482°C, fluidized with nitrogen for one min, then heated to approx. 650°C for two minutes under fluidization with hydrogen, then held at approx. 650°C for one min while fluidizing with nitrogen, then held at 650°C for 10 min while fluidizing with air, and then cooled to approx. 482°C during approx. 0.5 min while fluidization with air continued. After 10 such cycles, the catalyst was used in experiments carried out as described in example IV. The tin content of five catalysts together with the results of the experiments involving cracking of feedstock II at a catalyst/oil ratio of 7.7 are given in Table VIII.

Table IX shows the results from these catalysts obtained at 64% conversion, these were obtained from regression analysis curves derived from a large number of experiments with these catalysts.

As can be seen from the turnover column in the table

VIII, the cracking performance of the cracking catalysts was reduced when impregnated with dibutyltin oxide to any of the stated tin concentrations. As shown by the selectivity for gasoline column in Table IX, impregnation of the cracking catalyst with dibutyltin oxide increased its selectivity for gasoline production to some extent. It should be particularly noted that impregnation of the cracking catalyst to 0.1% by weight Sn increased the selectivity of the cracking catalyst for gasoline production by only 1% at a constant conversion of 64% by volume.'

The results are shown in table VIII bg IX.

Example VI

Six samples of catalyst I were treated so that

they contained different concentrations of tributylphosphine by impregnation of weighed portions with a solution of tributylphosphine in dry cyclohexane. After removal of the solvent by evaporation, the catalysts were used in

search with cracking of feed material III. These experiments were carried out in a fixed bed reactor at 482°C. The catalyst/oil ratio was adjusted to 75 volume percent conversion of the feed material.

The selectivity for petrol, the coke content and the hydrogen production were measured. All results were compared to those obtained with a catalyst containing no treatment agent, which was arbitrarily scored as 1.00. The selectivity for gasoline is defined as the volume of liquid products boiling below 204°C divided by the volume of converted oil multiplied by 100. The volume of converted oil is the volume of feed material minus the volume of extracted liquid boiling above 204°C. If e.g. the selectivity for gasoline of the untreated catalyst is 50% by volume, a selectivity for a treated catalyst of 1.04 in the following table means a selectivity of 52% by volume for this treated catalyst.

The coke content of the catalyst is measured by weighing the dry catalyst after the cracking process. The quantity of hydrogen produced is determined in standard equipment, where the hydrogen content of the gaseous products leaving the reactor is analysed.

The phosphorus content of these catalysts and the results

of the trials are given in Table X.

In particular, it should be noted that impregnation of the cracking catalyst to a level of 0.1 wt% P increased the cracking catalyst's selectivity for gasoline production by only approx. 2% at a constant turnover of 75 percent by volume.

Example VII

A sample of catalyst I was treated with P 2 S 5 by combining a weighed amount of the catalyst with a weighed portion of solid P 2 ^ 5 . These components were mixed by shaking. The resulting mixture was conditioned and aged as described in detail in Example V, and then used in an experiment where feed material I was cracked, as described in Example IV. The phosphorus content of this catalyst together with the results of tests conducted with it and a comparison catalyst are shown in Table XI.

As shown by the reduced catalyst/oil ratio, the addition of P2S5 increased the activity of the cracking catalyst for cracking the hydrocarbon feedstock. The process increased the cracking catalyst's selectivity for petrol production by approx. 3.9% on a turnover level of 74%.

Example VIII

A sample of catalyst I was treated with P2S5 t:"-l

a phosphorus level of 0.1% by weight P, exactly as described in Example VII. The treated cracking catalyst, after conditioning and aging, was used for fluid catalytic cracking of feed material II of approx. 510°C, followed by the procedure described in Example IV. The results are shown in Table XII.

The results stated above seem to some extent to

be contrary to the results shown in Table XI. In the experiments indicated in Table XII, it appears that the incorporation of ^ 2Ss into the ^ata-'-Ysator to some extent reduced the activity of the cracking catalyst for cracking the hydrocarbon feed material and reduced the selectivity of the catalyst for gasoline production at approximately the same conversion level by approx. 7.0%.

Example IX

A sample of catalyst II was impregnated with a cyclohexane solution of (C4Hg)2Sn(SCH2CO2CgH12)2 (Thermolite 31, commercially available from M&T Chemicals, Inc.) to a tin concentration of 0.011 weight percent and used for cracking feedstock III. After removal of solvent, the catalyst preparation was conditioned and aged as described in Example V. The catalyst, together with an untreated control sample, was used in experiments at different catalyst/oil ratios. These are indicated and the results of the trials are shown in Table XIII.

The impregnation of the cracking catalyst with Thermolite 31 to a tin level of 0.011 wt% Sn reduced catalyst activity, increased the catalyst's selectivity for gasoline production, increased coke production, and appeared to reduce hydrogen production at high conversion levels. At 70% conversion, the tin- and sulphur-treated cracking catalyst increased the selectivity for gasoline by 4.5%. At 75% turnover, the improvement was 2.9%. At 80% turnover, the improvement was 1.5%. Comparison of the results given in Table XIII with those in Table IX shows that the tin/sulphur treatment increased the catalyst's selectivity for petrol production to a far greater extent than treatment with tin alone. Based on the weight of added tin, it actually seems that the treatment of the catalyst with tin and sulfur in combination is at least 10 times more effective in improving the selectivity of the catalyst for petrol production than treatment with tin alone. Since an industrial cracking unit often has 200 tons or more of recycle catalyst, the increased effectiveness of tin and sulfur in improving the selectivity of the catalyst for gasoline production can represent a significant economic savings.

Example X

A sample of catalyst I was impregnated with tin(IV) di-n-propyl phosphorodithioate to a tin concentration of 0.1% Sn by weight. The weight ratio between the phosphorus and tin that was brought into contact with the cracking catalyst was approx. 1:1. The weight ratio between sulfur and tin that was brought into contact with the cracking catalyst was approx. 2:1. The weight ratio between phosphorus and sulfur that was brought into contact with the cracking catalyst was approx. 1:2.

The treated cracking catalyst was, after conditioning and aging as described in example V, used for fluid catalytic cracking of feed material II on

510°C, followed by the procedure used in Example IV. The results are shown in Table XIV.

Treatment of the cracking catalyst with tin, phosphorus and sulfur gave a small improvement in catalyst activity, reduced hydrogen and coke production and increased the catalyst's selectivity for petrol production at a slightly higher conversion level by approx. 11%. This is particularly surprising in view of the data set out in Tables IX and XIII. Impregnation of the same cracking catalyst in this example with the tin compound of Example V to a level of 0.1 wt% Sn improved the selectivity of the catalyst for cracking the same feedstock to gasoline by only about 1%. Impregnation of the same cracking catalyst in this example with P2Sj- as in Example VII to a level of 0.1 weight percent P reduced the selectivity of the catalyst for cracking the same feed material to gasoline by approx. 7.0% at a turnover level of 64%. It is noteworthy that the combined Sn-P-S treatment in this example provided an improvement in the selectivity of the catalyst for gasoline production of approx. 11%.

Example XI

In Example II of US-PS 4,101,417, a zeolite-containing cracking catalyst with 10,350 vanadium equivalents was deposited then impregnated with hexabutyltin to a level of 0.61 wt% Sn, and another sample was impregnated with stannous chloride to a tin concentration of 0.61 wt% Sn and then contaminated with 10350 vanadium equivalents. Because of. the high surface area, it does not appear that the catalyst treated according to the above cited patent was an equilibrium cracking catalyst. The hexabutyl tin treatment increased turnover by approx. 7.3% and the selectivity for petrol production by approx. 3.8% at the higher turnover level. The stannous chloride treatment increased turnover by approx. 13.7% and the selectivity for petrol with approx. 4.1% at the higher turnover level. The weight ratio between tin and vanadium equivalents on the cracking catalyst was approx. 0.6:1. In example X in the present description, the weight ratio between tin and vanadium equivalents on the cracking catalyst was approx. 0.047:1. In consideration of the apparent discrepancy between Example V of the present specification and Example II of US-PS 4,101,417, it should be noted that the catalyst used in Example V was an equilibrium cracking catalyst on which the metal deposits had accumulated during industrial use of the cracking catalyst , while on the cracking catalyst used in the US-PS 4,101,417 examples, recently deposited metals were present. It is believed that the propensity to be passivated by treatment agents is different for metals deposited on a cracking catalyst during cracking of metal-containing feedstock than it is for metals newly deposited by other means. The discovery that drastically improved catalyst selectivity for gasoline production was obtained by treating cracking catalysts containing equilibrium deposits of metals with tin and at least one of phosphorus and sulfur is particularly surprising in view of the rather poor performance of tin alone on the same cracking catalyst.

Example XII

A catalyst containing 0.10% by weight of tin was prepared by impregnating 40 g of catalyst I with 0.325 g of tin(IV) dipropyl phosphorodithioate in 40 ml of cyclohexane. The solvent was removed by evaporation and the dry catalyst placed in a vertical quartz tube reactor in a tube furnace. During fluidization with nitrogen, the catalyst was heated to 482°C. Nitrogen was replaced with hydrogen and the temperature increased to 649°C. Hydrogen was replaced with nitrogen and the catalyst fluidized for 5 min to flush the reactor, after which the catalyst was fluidized with air for 15 min at this temperature.

A catalyst containing 0.10% by weight of antimony and 0.01% by weight of tin was prepared by impregnating 40 g of catalyst I with 0.363 g of antimony(III) dipropyl phosphorodithioate and 0.033 g of the tin compound in 40 ml of cyclohexane. The solvent was removed by evaporation and the catalyst conditioned as previously described.

A catalyst containing 0.10 weight percent antimony was prepared as described immediately above, except that the addition of tin was omitted.

A sample of catalyst I and the three modified catalysts described above were used for cracking feed material II at 510°C in fluidized bed reactors. Atmospheric pressure was used with cracking periods of 0.5 min and intermediate regeneration periods at 649°C.

Before testing, each of the catalysts was aged by fluidizing in nitrogen at approx. 482°C for approx. 1 min, then heated to 510°C while fluidizing with hydrogen for 2 min, then fluidized with nitrogen at 510°C for 1 min, then fluidized with air at approx. 649°C for 10 min and then cooled to approx. 482°C under air fluidization for approx. 0.5 min. After 10 such cycles, the catalysts were cooled to room temperature under fluidization with nitrogen.

The results of the cracking tests are shown in the table

XV.

As can be seen from the data given in Table XV, the treatment of the cracking catalyst with tin and antimony di-n-propyl phosphorodithioate to obtain a weight ratio between tin and antimony in the catalyst of approx. 1:10, a synergistic improvement of at least the cracking activity of the catalyst.

A catalyst containing 0.10% tin by weight was prepared by dry mixing dibutyltin oxide (milled until it passed a 325 mesh sieve) with a portion of catalyst I. The mixture was wetted with cyclohexane and the resulting mixture brought to apparent dryness by heating at a hot plate. The catalyst was preconditioned and aged in the same way as described above and used for fluid catalytic cracking of feed material II as described above. A series of experiments was carried out at different catalyst/oil ratios and the results shown in Table XVI below are read from a smooth curve obtained by curve fitting the data points.

A catalyst containing 0.10 wt.% antimony and 0.01 wt.% tin was prepared by dry mixing dibutyltin oxide with a portion of catalyst I as described above, followed by impregnation with a mineral oil solution of antimony(II) dipropyl phosphorodithioate dissolved in cyclohexane instead of the above described wetting steps with cyclohexane. The resulting catalyst was then conditioned and aged as described above and used for fluid catalytic cracking of feedstock II as described above. A series of experiments was carried out with different catalyst/oil ratios and the results given in Table XVI are read from a smooth curve obtained by curve fitting the data points.

A catalyst containing 0.10% by weight of antimony was prepared as described above but with the difference that dibutyltin oxide was not first mixed with the catalyst.

A series of experiments was carried out with different catalyst/oil ratios and the results shown in Table XVI are read from a smooth curve fitted from the data points.

Comparison between the experiments in Tables XV and XVI where antimony and tin are used in combination gives no clue as to the surprising effectiveness of the particular tin compound which was tested for itself according to Table XV.

Claims (11)

1. Method for increasing the selectivity for gasoline production of a cracking catalyst used for catalytic cracking of hydrocarbons in the absence of antimony and in the presence of an agent for passivation of catalyst contaminating metals, characterized in that a tin thiophosphate with the general formula where each R is the same or different and means a hydrocarbyl group of 1-24 carbon atoms, each X is independently selected from oxygen and sulfur, at least one X being sulfur, and n being 2 or 4. 2 Method as stated in claim 1, characterized in that the passivating agent is used in an amount which provides a tin concentration of 0.01-0.15 percent by weight calculated on the cracking catalyst. 3. Method as stated in claim 1 or 2, characterized in that a tin thiophosphate with the general formula where R and n have the meaning stated in claim 1 is used as a passivating agent. 4. Process as stated in claim 1 or 3, characterized in that R is an ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, amyl, n -hexyl-, sec-hexyl-, n-heptyl-, n-octyl-, isooctyl-, tert-octyl-, cyclopentyl-, cyclohexyl-, dimethylcyclohexyl-, diethylcyclohexyl-, phenyltolyl-, cresyl-, ethylphenyl-, butylphenyl- , amylphenyl, octylphenyl or vinylphenyl group. 5. Method as set forth in claim 3, characterized in that tin(II) di-n-propyldithiophosphate is used as a passivating agent. 6. Method as stated in claim 3, characterized in that tin(IV) di-n-propyldithiophosphate is used as passivating agent. . 7. Procedure as specified in claim 6, characterized in that the cracking catalyst is impregnated with a solution of the aforementioned tin(IV) di-n-propyldithiophene etc. 8. Method as stated in one of the preceding claims, "characterized in that the passivating agent is introduced into the cracking process together with the hydrocarbon feed material. 9. Procedure as stated in claim 8; characterized in that the passivating agent is dissolved in the hydrocarbon feed material to give it a tin concentration of 1-200 parts of tin per million parts feed material. 10. Method as stated in one of the preceding claims, characterized in that the passivating agent is used in such an amount that the weight ratio between tin and vanadium equivalents on the cracking catalyst lies between 0.5:100 and 50:100. 11. Method as stated in one of claims 1-7, characterized in that: (a) a hydrocarbon feed material is brought into contact with a fluidized zeolite-containing cracking catalyst in a cracking zone under cracking conditions in the absence of added hydrogen and antimony to obtain a cracked product, ( b) the cracked product is removed, (c) the cracking catalyst is fed from the cracking zone to a regeneration zone, (d) the cracking catalyst is regenerated in the regeneration zone by contact with an oxygen-containing gas under regeneration conditions for the production of a regenerated catalyst, (e) the regenerated catalyst is fed into the cracking zone for contact with the hydrocarbon feed material, the regenerated catalyst containing impurities selected from nickel, vanadium and iron deposited on the cracking catalyst in such a way that it cannot be fully regenerated in the regeneration zone, and (f) contacting the cracking catalyst with the passivating agent .